Trust Instincts in Teens are Faulty

Posted on April 7, 2014 at 8:12 pm

Teenagers who follow their gut when making a quick decision may actually make poor decisions.[1] In a teenager, the limbic system—or the part of the brain that affects emotion, behavior, and motivation—has yet to fully develop, as that happens during adulthood.1

“We know adolescence is a time of profound social change,” said Kevin LaBar, PhD, a professor at the Duke Center for Cognitive Neuroscience. “It is also a profound time for risk-taking—a time period when peer influence is more important. This is when we start establishing independent relationships with adults, and some of those relationships are going to be influenced by how trustworthy those people are. It is important in these relationships to evaluate who you can and can’t trust. To date, there has been significant research into how the adult brain processes and judges trustworthiness, but few studies look at the adolescent brain’s ability to evaluate trustworthiness.”1

Therefore, LaBar and colleagues conducted a study to examine the capability to evaluate trustworthiness in adolescent girls, ages 10 to 20.1 Boys were not included, as they mature at a slower rate.1 Forty-three girls were shown 34 pictures of adult faces in quick glimpses (50- to 100-millisecond) while their reactions were recorded in real time using fMRI brain scanning.1

“After each flash, the images were immediately scrambled to prevent the girls from developing any lasting visual memory of a face,” said LaBar.1

After each image, the participant rated the face as one of the following: very untrustworthy, untrustworthy, trustworthy, or very trustworthy.1 The fMRI scans helped the researchers isolate the regions of the brain that were responsible for processing social and emotional information from faces.1

Researchers found that faces with downward-turned mouths and furrowed brows were among the most untrustworthy, while those with U-shaped mouths and wide-set eyes were among the most trustworthy.1 fMRI results showed that the amygdala—which evaluates negative emotions—and the insula—which plays a role in gut-level decision-making—were the most active when the untrustworthy faces were shown.1 These areas of the brain are components of the limbic system.1

The right amygdala showed high levels of activity when participants were shown untrustworthy faces; however, other spots within the amygdala and insula also showed increased activity during this time, especially among 13- to 15-year-old participants.1

“These heightened responses for untrustworthiness suggest that during this time, girls at this age are particularly sensitive to the facial features they feel are untrustworthy,” said LaBar. “We don’t know why. Maybe it is a post-pubertal hormone change that brings on the heightened response or maybe they are more motivated to scan for social threats during this period.”1

fMRI results also found that during mid-adolescence, the amygdala was still active, yet showed a reduced connectivity with other parts of the brain that is involved in facial processing.1

“Rather than these areas working in sync, participants this age experienced enhanced limbic system (emotional and behavioral) responses and a greater disconnection from brain regions that could help regulate responses,” said LaBar. “This disconnect can lead mid-adolescents to process untrustworthiness in different ways. If you look at mid-adolescents, they don’t rate trustworthiness the same as adults or younger or older adolescents. There are clearly some changes happening in the mid-adolescent brain in how regions talk to each other, and can lead to behavioral differences in how trust is established.”1